The present invention relates to smoking articles such as cigarettes, and in particular to cigarettes which generate low amounts of visible sidestream smoke.
Popular smoking articles such as cigarettes have a substantially cylindrical rod shaped structure and include a charge of smokable material such as shredded tobacco (eg., cut filler) surrounded by a paper wrapper thereby forming a so-called "tobacco rod." Certain commercially available cigarettes have cut filler which comprises a major amount or a total amount of flue-cured tobacco material. Often, the use of low nitrogen content cut filler materials is desirable in order to achieve certain smoking characteristics. It has become desirable to manufacture cigarettes having cylindrical filter elements aligned in an end-to-end relationship with the tobacco rod. Typically, filter elements are manufactured from fibrous materials such as cellulose acetate and plug wrap, and are attached to the tobacco rod using a circumscribing tipping material.
Cigarettes are employed by the user by burning one end thereof. The user then receives mainstream smoke into his/her mouth by drawing on the opposite end (eg., the filter end) of the cigarette. During the time that the cigarette is not being drawn upon by the user, it remains burning, and sidestream smoke can be generated. Sidestream smoke is smoke which directly enters the atmosphere during the static burn period of a smoking article. Sidestream smoke diffuses into the atmosphere, and the characteristic visible nature thereof may be perceived negatively by certain individuals.
The so called "full flavor" cigarettes have been popular smoking articles which deliver a desirable tobacco taste, flavor and satisfaction to the smoker. Typically, the "full flavor" cigarettes deliver about 14 mg or more of FTC "tar" per cigarette. Cigarettes also can be classified as "full flavor low tar" cigarettes. Typically, the "full flavor low tar" cigarettes deliver from about 8 to about 14 mg of FTC "tar" per cigarette, as well as lower levels of FTC nicotine as compared to "full flavor" cigarettes. Yet another classification of popular cigarettes is the "ultra low tar" cigarette which delivers still lower levels of FTC "tar" and nicotine. Typically, the "ultra low tar" cigarettes deliver less than about 7 mg of FTC "tar" per cigarette. The "full flavor low tar" and "ultra low tar" cigarettes conventionally have air dilution means such as laser perforations provided in the periphery of the mouthend region thereof, or have filter elements highly efficient for the removal of "tar" and nicotine from the mainstream aerosol. In general, the perceived taste or strength of the cigarettes classified as having lower levels of "tar" and nicotine are progressively less than that of the cigarettes which are classified as approaching the characteristics of the "full flavor" cigarettes.
Recently, consumers of cigarettes have tended to demand an increased selection of various "full flavor low tar" and "ultra low tar" cigarettes. Such cigarettes have flavor patterns which are milder than those flavor patterns characteristic of either "full flavor" cigarettes or cigarettes which were marketed in the past. However, the presently popular lower "tar" cigarettes have achieved consumer acceptance because the taste and smoking satisfaction provided by such cigarettes have remained high. In addition, certain consumers have indicated a desire to decrease the levels of visible sidestream smoke generated by their cigarettes.
U.S. Pat. No. 4,637,410 to Luke proposes a cigarette having a circumference of from 10 mm to 19 mm. At col. 2, lines 5-7 of the reference, it is disclosed that the proposed cigarettes exhibit lower smoke component mainstream and sidestream deliveries.
U.S. Pat. No. 4,624,268 to Baker et al proposes a cigarette having wrapper paper with an inherent air permeability of 3 to 45 CORESTA. For example, the wrapper paper is disclosed as having a coating of starch, aluminum oxide, magnesium oxide, calcium oxide, sodium formate and sodium acetate. See col. 3, lines 23-37. However, such a cigarette would be expected to yield mainstream smoke having a relatively high gas phase content.
Certain references suggest that certain gases can be removed from the mainstream smoke of cigarettes. For example, Avedikian in U.S. Pat. No. 3,368,566 proposes a cigarette having a plurality of short filters which individually contain certain substances for the supposed removal of various substances from mainstream cigarette smoke. Another cigarette having a less complicated filter design than that design proposed by Avedikian is proposed by Brooks in U.S. Pat. No. 4,481,960. Although Brooks proposes a cigarette having (i) a paper wrap with the possibility of a wide range of air permeability, and (ii) air dilution such that the yield of mainstream carbon monoxide is relatively low, the reference does not address a cigarette yielding a low level of visible sidestream smoke.
U.S. Pat. No. 4,231,377 to Cline et al, U.S. Pat. No. 4,420,002 to Cline, and U.S. Pat. No. 4,450,847 to Owens propose that cigarette paper wrappers containing magnesium oxide and/or magnesium hydroxide materials can be used in order to manufacture cigarettes which yield reduced visible sidestream smoke during static burn periods. However, such low permeability paper wrappers can tend to provide an off-taste to mainstream smoke or an undesirable aroma to sidestream smoke.
It would be desirable for the cigarette manufacturer to provide a good tasting cigarette which meets the desires and demands of certain smokers or groups of smokers. In particular, it would be desirable to provide a good tasting cigarette which delivers the characteristic mild taste of low "tar" cigarettes, provides good smoking satisfaction, provides low mainstream gas phase deliveries, and which generates low levels of visible sidestream smoke.